MASS, VOLUME, AND DENSITY HOW TO MAKE LIQUIDS LAYERED!

Transcription

1 MASS, VOLUME, AND DENSITY HOW TO MAKE LIQUIDS LAYERED!

2 MASS A measurement of the amount of matter in an object Can be measured with a triple beam balance or electronic balance It is measured in grams!

3 VOLUME The amount of space an object takes up. There are several ways to calculate volume. We are going to look at the ruler method and the water displacement method.

4 USING A RULER Just a quick reminder We only measure in the metric system in this class!!!! So How do we find the volume of an object using a ruler?

5 VOLUME BY RULER Length x Width x Height Used when the object has a REGULAR shape! Height Width Length

6 VOLUME BY RULER Our formula looks like this: L x W x H Height = 2 Length = 4 What is the answer?

7 VOLUME BY RULER If you said 24: You would be wrong! Why? Volume is measured in centimeters cubed = cm 3 Therefore, the correct answer would be 24 cm 3 Don t forget the units!!!!

8 How many of you have every gotten into the tub only to find out you have filled it too high and water flows over the top?

9 WATER DISPLACEMENT Well what is this? What types of object are you going to use water displacement on? Irregular!

10 WATER DISPLACEMENT Place a known amount of water into the graduated cylinder How much water is in this graduated cylinder? 20 ml

11 WATER DISPLACEMENT Very carefully place your object into the graduated cylinder what are some things you need to be aware of as you place the object into the graduated cylinder? Don t drop it directly into the graduated cylinder tilt the cylinder to the side and slide it to the bottom GENTLY!!!! Only place enough water in the graduated cylinder to cover the object by several ml. What should you do next?

12 WATER DISPLACEMENT Read the volume of the water after the object has been put in, then Subtract your beginning water level from your ending water level! 25 ml 20 ml 5 ml Ending Water Level -Beginning Water Level Volume of the object

13 JUST TO REVIEW If you have a regular uniformly shaped object that has a measureable length, height and width, we use which method of calculating volume? Ruler method If the object is irregularly shaped, then we use what method to calculate volume? Water displacement method

14 DENSITY Density is the amount of matter that is packed into a specific space. It is the mass of a substance divided by its volume Density Expression Density = mass = g or g or g/cm 3 volume ml cm 3 Note: 1 ml = 1 cm 3

15 DENSITIES OF COMMON SUBSTANCES

16 CALCULATING DENSITY

17 EXAMPLE Osmium is a very dense metal. What is its density in g/cm 3 if 50.0 g of osmium has a volume of 22.2 cm 3? A g/cm 3 B g/cm 3 C. 111 g/cm 3

18 SOLUTION Step 1 State the given and needed quantities. Given: 50.0 g; 22.2 cm 3 Need: density, g/cm 3 Step 2 Write the density expression. D = mass volume Step 3 Express mass in grams and volume in ml or cm 3. Mass = 50.0 g Volume = 22.2 cm 3 Step 4 Substitute mass and volume into the density expression and calculate. D = 50.0 g = g/cm cm 3 = 22.5 g/cm 3 (rounded to 3 SFs)

19 VOLUME BY DISPLACEMENT A solid: Completely submerged in water displaces its own volume of water Has a volume calculated from the volume difference Example: 45.0 ml 35.5 ml = 9.5 ml = 9.5 cm 3

20 DENSITY USING VOLUME DISPLACEMENT The density of the zinc object is calculated from its mass and volume. Density = Mass Volume = g 9.5 cm 3 = 7.2 g/cm 3

21 LEARNING CHECK What is the density (g/cm3) of 48.0-g sample of a metal if the level of water in a graduated cylinder rises from 25.0 ml to 33.0 ml after the metal is added? A g/cm 3 B. 6.0 g/cm 3 C. 380 g/cm ml 33.0 ml object

22 SOLUTION Step 1 State the given and needed quantities. Given: 48.0 g Volume of water = 25.0 ml Volume of water + metal = 33.0 ml Need: Density Step 2 Write the density expression. Density = mass of metal volume of metal

23 SOLUTION Step 3 Express mass in grams and volume in ml or cm 3. Mass = 48.0 g Volume of the metal is equal to the volume of water displaced. Volume of water + metal = 33.0 ml Volume of water = 25.0 ml Volume of metal = 8.0 ml

24 SOLUTION Step 4 Substitute mass and volume into the density expression and calculate the density. Density = 48.0 g = 6.0 g = 6.0 g/ml 8.0 ml 1 ml

25 SINK OR FLOAT Ice floats in water because the density of ice is less than the density of water Aluminum sinks because its density is greater than the density of water

26 LEARNING CHECK Which diagram correctly represents the liquid layers in the cylinder? Karo syrup (K) (1.4 g/ml); vegetable oil (V) (0.91 g/ml); water (W) (1.0 g/ml) A B C V W K W K V K V W

27 PROBLEM SOLVING USING DENSITY Density can be written as an equality. For a substance with a density of 3.8 g/ml, the equality is 3.8 g = 1 ml From this equality, two conversion factors can be written for density. Conversion 3.8 g and 1 ml factors 1 ml 3.8 g

28 PROBLEM SOLVING USING DENSITY

29 LEARNING CHECK The density of octane, a component of gasoline, is g/ml. What is the mass, in kg, of 875 ml of octane? A kg B. 614 kg C kg

30 SOLUTION The density of octane, a component of gasoline, is g/ ml. What is the mass, in kg, of 875 ml of octane? Step 1 State the given and needed quantities. Given: Needed: Density of octane = g/ml Volume = 875 ml Mass of octane Step 2 Write a plan to calculate the needed quantity. Density Conversion factor Plan: milliliters grams kilograms

31 SOLUTION The density of octane, a component of gasoline, is g/ml. What is the mass, in kg, of 875 ml of octane? Step 3 Write equalities and their conversion factors including density. density and g = 1 ml 1 kg = 1000 g Step 4 Set up problem to calculate the needed quantity. 875 ml x g x 1 kg = kg 1 ml 1000 g Answer is A, kg.