Heat

Investigation 5 part 3

EQ. How are changes in matter accompanied by changes in

energy?

• We have learned a great deal about this but there is more……

Today’s Focus

• LEQ 21 Explain how to calculate the energy transferred from the hot water particles and the energy gained by the cold water particles. Discuss their relationship.

What is a calorie?

• Open lab manual to page 48 “Calculating heat in Calories A”

• Read information

Is there a pattern?

• Change in temperature

• ΔT=Tfinal – Tinital

• Calculate calorie

• Mass X ΔT = cal

Cal=

• Cal = m X ∆T

• Calories = mass X change in Temperature

A Heat Transfer Experiment

• Last time we mixed water because we wanted to find out what temperature the final mix would be.

• Today, I want to find out how much heat transferred from the hot water to the cold water and how much heat transferred to the cold water during the mixing.

Heat Transfer

• Open to Lab Manual page 51

• Information/Data to enter

• Columns 1-6

Mass

• What is the relationship between mass and volume of water?

• 1 mL = 1 cm3 = 1 g Mass volume

This is only true for water

Experiment Procedure

• Get 50 mL of hot water in one foam cup and 50 mL of cold water in second foam cup

• Decide on the mass of hot water and the mass of cold water you will use. (need to be the same)

• Measure the water with the graduated cylinders.

Procedure

• Record their masses and starting temperatures in the table

• Immediately pour the cold water and the hot water in the third foam cup. Put that foam cup into a 500 mL cup for stability

• Quickly measure and record the final temperature.

Remember

• Act quickly after you record the starting temperature

• Immediately mix the samples and take the final temperature

• You have 10 minutes!

• Clean Up

CLEAN UP

• Dump water in sink

• Dry all materials completely

• Return tray with all materials

RESULTS

• What happened when you mixed the hot and cold water?

• The mixture reached a temperature that was between the hot and cold water temperatures.

Results-

• What caused the kinetic energy to change?

• Energy (heat) transfer as a result of particle collisions. Energy transferred from hot water particles to cold water particles until the kinetic energy was the same for all the particles

Results--

• Did energy transfer from the hot water or from the cold water?

• Energy transfers from the particles in the hot water. Energy flow is always from higher kinetic energy to lower kinetic energy.

Groups TPS

• How many calories were transferred from the hot water?

• How many calories were transferred from the cold water?

• What does that tell you about energy transfer?

Conservation of Energy

• Energy is conserved

• The amount of energy in a system is always the same

• No energy is ever created, and no energy is ever destroyed.

• Energy is transferred.

Energy transfer

• From one place to another

• From one kind of energy to another kind of energy

Equilibrium• Hot and cold mix and particles collide • Energy transfers from high energy particle to

low energy particle (from hot to cold from fast to slow)

• Transfer continues until the volume of water is all moving the same speed with same amount of kinetic energy

• The number of particles losing energy = the number of particles gaining energy (energy lost = energy gained)

• System is balance, no net energy transfer equilibrium is reached temperature holds steady.

Class work

• Complete LM page 52-53

• Mid Summative TEST Wednesday